Type bar rest pad



Oct. 18, 1955 R. D. DODGE ET Al.

TYPE BAR REST PAD Filed Dec. 31, 1952 TORS 1701765 MIL/WE. PA FYO/i/V B y: Er

INVEN lPfl/VALD 17.

lvm RN United States Patent Ofiice 2,729,959 Patented Oct. 18, 1955 TYPE BAR REST PAD Ronald D. Dodge, Poughkeepsie, Ralph E. Page, La-

grangeville, and John H. N orcross, Poughkeepsie, N. Y., assignors to International Business Machines Corporation, New York, N. Y., a corporation of New York Application December 31, 1952, Serial No. 329,028 Claims. (Cl. 197-42) This invention relates to typewriters, and more particularly to an improved typewriter basket structure for absorbing the shock resulting from type bars striking the basket as they return to their rest position after a print stroke.

In conventional typewriter design, a basketa somewhat U-shaped metal stripis utilized to support type bars in their normal or rest position. Usually some shock absorbing medium is positioned between the bars and the basket contiguous with the latter to reduce to a minimum the detrimental effects (i. e. noise and type bar rebound) resulting from the type bar striking the basket after a print stroke.

The advantage of noise elimination is, of course, self explanatory and the elimination of type bar rebound is significant since the degree of rebound determines to some extent the speed at which a typewriter can be operated. Specifically, if a type bar rebounds upon contact with the basket, then it might collide with a second type bar being driven into a print position. Further, if a type bar is not in its rest position at the start of a print strokea condition which might occur for a repeat strokethen the type bar will not get the impetus of the initial driving force of the power roll, and this initial force is of major value in determining the power of a particular print stroke, and the consequential color density of the imprinted character. The speed of the machine is involved since one simple way of reducing the possibility of type bar collision and of insuring uniform print color density is to allow the type bar adequate time to oscillate to rest position before the next type bar is started on a print stroke.

Through studies of type bar motion, it has been determined that the ultimate in anti-rebound characteristics will be attained when a construction is presented wherein all the energy of the returning type bar is transferred at the moment of its impact to the basket. For such energy absorption, it is necessary that the basket absorb the energy of the type bar either through the inherent absorbing ability of its material, or that it be put into motion by the shock energy from the type bar.

Type bar motion study has determined further that the noise level of rebounding type bars is proportional to the area of impact between the returning type bar and the basket. That is, for any one machine, the noise level made by the type bars returning to their rest position is directly proportional to the area of contact between the type bars and the basket rest pad.

While many U. S. patents have been granted for typewriter baskets which reduce noise or which decrease type bar rebound, industry, in its ceaseless efforts to produce a typewriter which will provide the ultimate in customers satisfaction, is still seeking a typewriter construction which will reduce both noise level and degree of rebound to a minimum, and accordingly, it is an object of this invention to provide an improved typewriter basket wherein type bar noise and rebound is reduced to a minimum.

It is a further object of this invention to provide an improved typewriter basket wherein substantially all the energy of the returning type bar is transferred to the basket at the moment of impact.

It is a still further object of this invention to provide a new and improved typewriter basket construction wherein the noise level produced by a returning type bar is reduced to a minimum without increasing the degree of rebound of the bars.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

Briefly, this invention relates to an improved typewriter basket which comprises a resilient element supported for movement in a plane which includes the direction of lines of force imparted to the basket by the type bars at the instant of contact, and a load spring which lies in juxtaposition with the surface of the resilient element, opposite the type bar impact surface. The function of the spring is to add to the shock absorbing ability of the resilient element and to center the resilient element whereby it will be properly positioned to receive each descending type bar.

In the drawing:

Fig. l is a front elevation of the improved typewriter basket construction including several type bars shown in their rest position.

Fig. 2 is a vertical sectional view taken through the plane of the line 2-2 of Fig. l in the direction of the arrows.

Referring to the drawing, and particularly to Fig. 2, the basket 1 is shown comprising basically a resilient element 2, a support or guide 3 and a spring unit 4.

Resilient element 2, which preferably is made of a rubber or rubberlike material, is arcuately shaped and has, in cross section, an upper curved surface 5 providing minimum contact area with a type bar 6. The lower edge of the element 2 is recessed at 7 so as to fit over the spring unit 4 as shown, and the sides 8 and 9 of the element lie in parallel planes.

It will be appreciated that any reduction in the area of contact between a type bar and its support contributes materially to the reduction of noise level from type bar impact, but it also tends to produce an objectionable rebound in the type bar unless the support is designed to absorb the impact of the bar. In order to absorb the impact, support 3 has been provided to house the resilient element 2, and to support it for radial, shock absorbing movement in response to type bar impact. The support 3 comprises parallel, arcuate shaped guide elements or plates 10 and 11 which are positioned respectively at the sides 8, 9 of the resilient element 2. Formed in the plates 10, 11 are aligned apertures or openings 12 at spaced arcuate positions, and at least one of the plates is provided with a plurality of fingers 13 which, preferably, are punched from the plate to extend through motion limiting slots 14 in the resilient element 2, and through a corresponding one of the aligned openings 12 in the opposite plate. At the ends of the fingers 13 are bifurcated portions 15 which are bent over, as shown, to support plates 10, 11 in parallel spaced alignment. Obviously, the finger ends 15 could be tack welded or otherwise secured to the plate 11 to maintain a predetermined spacing between the parallel plates. In this manner, the fingers 13 perform a dual function, namely, they space plates 10, 11 and they serve as motion limiting stops when in engagement with a portion of the periphery of slots 14. The ends of the guide plate 10 extend beyond the ends of the plate 11, as shown in Fig. 1, and are connected to rods or projecting portions 17 of the typewriter frame. It will be appreciated that this mounting of the plate 10 and the connecting of the plate through the fingers 13 to the plate 11, provides a rigid supporting or guide structure 3.

With the arrangement of the type bars as shown, it should be noted that the effect of gravity on the descending type bars decreases between the center and outer ends of the basket; that is, since the center bars a fall vertically while the outer bars have a considerable horizontal direction vector, the force of gravity has less restoring effect on the outer bars. It follows that it is not necessary for resilient element 2 to move as far for shock absorption at its outer ends as is required at the center. Accordingly, the slots 14 in the resilient element 2 do not need radial dimensions at the outer arcuate extremities as great as those required for the central slots, but for convenience all the radial dimensions of the slots are shown in Fig. l as being substantially equal.

The spring unit 4, which is positioned beneath the resilient element 2 and in peripheral contact with the recessed portion 7, tends to bias the element 2 radially inwardly. The fingers 13,.extending through the slots 14, however, limit the radially inward movement of the element 2 and, consequently, the spring unit 4 holds the lower edges of the slots 14 normally in engagement with the fingers 13, as shown in Figs. 1 and 2.

The spring unit 4 comprises a coiled spring 18 which is connected at its ends to ears 20 and 21 formed on the ends of the plate 10. Surrounding the spring 18 is a flexible tubular member 22 formed by a wire which is wound in a direction opposite .to that of the spring 18. The member 22 fits loosely over the spring 18 and is received within the recess 7 of the resilient element 2, the member extending substantially the full length of the element. Resistance between the element 2 and the member 22 is sufficiently great to prevent movement of either one relative to the other, but the member 22 slides freely along the spring 18. This free sliding movement is made possible by the small contact area obtained between the member 22 and the spring by reason of the turns extending in opposite directions. The ends of the spring 18 extend beyond the ends of the element 2 so that the latter is free to move with the member 22 out of a centered position if the action of to produce such movement. The weight of the element 2 and the member 22 operates continuously to urge them toward a centered position.

In the normal position of the parts, as shown in Fig. 2, the element 2 is held by the spring 18 so that the bottoms of the openings 14 are held against the fingers 13. The top of the element extends far enough above the guide plates so that the impact of a type bar is insufficient to move the element downwardly far enough to engage the type bar with the guide plates. Engagement of any one of the type bars with the element 2 causes the latter to be compressed slightly at the point of impact, but the element moves downwardly against the action of the spring 18 so that the recovery of the ment and does not cause the type bar to rebound. The spring 18 is relatively weak, and the combined weight of the element 2 and the member 22 is such that a mini- -mum vibration is obtained.

It has been mentioned, hereinabove, that the minimum contact area of arcuate surface tends to produce "a rebound'in the returning type bar 6. Because of the spring suspension provided for the element 2 by spring unit 4, a returning type bar transfers substantially all its shock energy to the resilient element 2 to put the oscillate to an extent that would disturb the type bars in their rest position.

With this improved basket construction, it has been found that the noise level of a typewriter is reduced the type bars tends resilient element is counteracted by its downward movep materially and, simultaneously, the rebound of keys returning to the basket is kept at a minimum whereby an improved typewriter is produced.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. An improved typewriter basket for supporting type bars in their rest position comprisi g a resilient flat Sid d arcuate shaped element having a curved surface at its inner edge and a recessed surface at its outer edge with said curved surface being engageable by said type bars, guide means suporting said element for radial movemen in a plane including the direction of lines of force of impacting type bars, a spring unit engaging said recessed surface along the entire length for urging said element radially inwardly, and stop means on said guide means to limit the radially inward movement of said resilient element, said spring unit comprising a coil spring and a. flexible tubular member fitting loosely over said spring.

2. An improved typewriter basket for supporting type bars in their rest position comprising a resilient arcuate shaped fiat sided element having a plurality of transverse slots, said resilient element also having a rounded surface at its inner edge and a recessed surface at its outer edge, guide means positioning said resilient element for radial movement in a plane including the direction of lines of force of impacting type bars, said rounded surface being positioned for contact by said type bars, said guide means comprising parallel arcuately shaped plate means positioned contiguous said resilient element on opposite sides thereof, said plates having apertures positioned in align ment with said slots, at least one of said plates having fingers extending therefrom respectively through one of said slots and a corresponding one of said aligning apertures, means holding said plates in parallel spaced relationship, and a spring unit positioned for peripheral contact with said resilient element to urge the same radially inwardly until the peripheries of said slots engage said fingers, said spring unit comprising a coil spring connected to the opposite ends of one of said plates, and a flexible tubular member fitting loosely over said spring and engaging the recessed surface of said resilient elemen 3. The mechanism of; claim 2 wherein said tubular member is formed by a wire wound in a direction oppositc to that of said spring.

4. improved typewriter basket for supporting type bars in their rest position comprising a resilient arcuate shaped element, means loosely guiding said element, for movement in the direction of lines of force of impacting type bars, a recessed surface on said element at its edge farthest from said type bars, a resilient tubular member received within said recessed surface, and a coil spring extending loosely through said tubular member and connected at its ends to said guiding means for yieldingly supporting said element.

5. The mechanism of means comprises va pair of parallel plates arranged at the sides of said. lement, supporting members extending between said plat s, and spaced op nings in said elemen loosely re eiving said supporting members.

References Cited in the, file of this patent STATES PATENTS 884,347 Yetman Apr. 7, 1908 2,043,393 Pasinski June 9, 1936 2,176,123 Denzer Oct. 17, 1939 claim 4 in which said guiding 

